Difference between the absolute thermodynamic temperature scale and ITS-90

[Ronalds]

Homework Statement

What is the difference between the absolute thermodynamic temperature scale and the practical temperature scale: ITS-90?

Homework Equations

The Attempt at a Solution

 

[jtbell]

Do you want to know the conceptual difference between the two scales, or do you want to calculate the (numerical) difference between them?

 

[Ronalds]

I wanted to know the conceptual difference between the two scales. Is there anything else except that ITS-90 is a calibration standard for the thermodynamic temperature scale, not a scale itself? Could you please tell in your own words, without any links to bunch of information. Would really appreciate it!

 

[jtbell]

ITS-90 is a "practical" temperature scale, defined in terms of real devices that you can use in a laboratory. Thermodynamic temperature is an "ideal" scale, defined using the laws of thermodynamics. In order to make measurements using it, you would need to use devices that don't exist in practice, e.g. ideal gases or Carnot engines.